On Linux, previous versions of Elasticsearch defaulted to using /tmp as the
temporary directory for the process. However, /tmp is public so we have
elected to change the packaging so that we use a private temporary directory. If
you are upgrading from a previous version of Elasticsearch and preserve your
existing jvm.options, you should add the line
-Djava.io.tmpdir=${ES_TMPDIR}. It is safe to do this on all OS as we preserve
using a private temporary directory on non-Linux systems with the same
mechanism.